• 13.8 baseline — 0.6 × season 13.4 (15 gm) + 0.4 × last 10 14.3
• +0.2 opponent leak — they concede 157.2/game vs a 155.4 league average
• −2.9 at this ground — averages 10.9 there (7 gm)
• vs them: averages 11.4 over 9 games — evidence, never summed

Derived, not measured — plain arithmetic over his real games, shown in full. Adjustments can overlap (a game at this ground can also be a wet one); they add simply, and this note is the admission. Round 7: 25 — far outside his usual range; kept in the average, not smoothed away.